Morphogenetic effects resulting from exposure to abnormally high temperatures during the embryogeny of Aedes aegypti are currently being investigated in an attempt to elucidate the phenomenon of thermally induced unilateral and bilateral sterility that occurs in adults of both sexes of this mosquito. Mating competitiveness and oviposition will be examined as well as genetic analyses of offspring produced by reciprocal crosses and out-crosses of unilaterally sterile individuals. The information obtained could well be used as a new approach to implement biological control singly or in conjunction with another factor of mosquito population control using Knipling's principle of applied sterile techniques. Because the stressed embryo represents a potentially sterile adult, a practical ecological method of mixture with feral individuals in the egg as well as the larval, pupal and adult stage of development may be effected.